Digital-to-analog converters are used to convert digitally coded signals to an analog signal, or in conjunction with successive approximation circuitry as part of an analog-to-digital converter. DACs may employ a voltage applied across a resistor string or a current driven resistor string. Switches, such as transistors, couple intermediate taps at the resistor junctions, and sometimes at the resistor-potential junctions, to an output node. The digitally coded signal is decoded to determine which switches to turn on. The magnitude of an analog voltage produced at the output node depends on which switches are turned on. Heretofore, for each digital input and corresponding required analog output, a separate resistor string was required.
What is needed is a digital-to-analog converter that can utilize a single resistor string to provide multiple analog outputs, with each analog output corresponding to a digitally coded signal provided as an input.